I've had the 1920's and the 1930's bottlings. Pleasant enough Macallans.
Michael Jackson scores them all reasonably equally; Jim Murray gave the 1930's a big thumbs up, but was pretty critical of the others.
However, they've been out for some time, and bottlings (particularly from Macallan) have been pretty variable, so don't let an old negative review put you off - chances are, what you purchase today will be very different whisky to what both MJ and JM reviewed.
Personally, I think your grandfather will be thrilled with the bottle and the concept, regardless of the quality of the malt inside.